The present invention relates to the layout for a rotary device (e.g., a rotational molding system), comprising a manipulation station (e.g., a loading and unloading station), a heating chamber, a cooling chamber and the support of at least one tool such as a machine tool or mold for melting or casting workpieces particularly of plastics.
With this kind of layout plastic hollow articles can be manufactured by melting and casting corresponding to the shape of the tool by means of the rotation process.
In a known layout the tool is filled with the required plastics powder on the manipulating station and upon closing by means of the rotary device the tool is put in double rotary motion about two shafts which are vertical relative to each other. By means of a special layout having three working arms arranged radially about a center, a heating chamber, at least one cooling chamber and a manipulating station being joined in tandem on a circle around this center the filled and closed tool is rotatably swung with one working arm into the heating chamber. At the same time, another tool having previously been in the heating chamber is removed by means of a second arm and moved into the cooling chamber while it is still rotating. A further tool is conveyed by means of the third arm from the cooling chamber to the manipulation station, on which the tool or the mold is opened and the finished workpiece is removed. With this type of layout, workpieces having the most varied shapes and sizes can be produced.
Repeatedly divided tools for increasingly more complex workpieces, numerous tool inserts for molded-on connecting pieces, threads, tube nozzles, and the like, as well as various adjusting pieces in the form of nuts, sleeves, flanges, etc., result in increasingly longer manipulation times on the manipulating station while the heating times can be reduced.
The cooling times for the individual articles can vary quite substantially. In this layout two arms must subordinate themselves to the technologically cogent predetermined single cycle time of the third arm and, therefore, disadvantageously they can almost never run with their optimal cycle times.
In conventional layouts this kind of varied article program with possibly different cycle parameters and increasingly smaller manufacturing lot sizes and thus increased assembly steps results in unfavorable degrees of machine utilization and thus increases the production costs.